The present invention relates to a microchip-type oxygen gas sensor based on differential potentiometry. The microchip-type oxygen gas sensor according to the present invention comprises a working electrode and a reference electrode, wherein the working electrode is comprised of cobalt-plated electrode, a buffered hydrogel and ion-selective gas-permeable membrane, and the reference electrode is comprised of a Ag/AgCl electrode, which is non-sensitive to oxygen gas and an ion-selective gas-permeable membrane. The present invention also relates to a multi-sensor being capable of detecting two or more ions or gas species on a single chip.
Oxygen gas is one of essential factors to aquatic livings and human beings, and the quantification of the content of oxygen gas is of concern in a physiological field, a industrial field and the environmental field.
Conventional techniques for the quantification of the content of oxygen gas are largely classified into two categories; an optical method and an electrochemical method.
The optical method quantitatively measures how much oxygen gas has quenched photons emitted from fluorescent or phosphorescent material. Alternatively, it measures the variance of absorption caused by the formation of the reversible bond to oxygen gas. However, the optical method has a disadvantage that it requires very expensive instruments such as light source, spectrometer, etc. As thus, an electrochemical method has been widely used.
Currently, Clark-type amperometric sensors, galvanic sensors, and solid-state electrolyte potentiometric sensors have been used in the electrochemical method. However, the Clark-type sensors and the galvanic sensors have several disadvantages, for example, difficulty in fabrication of a microchip-type sensor. Based on being stable signals, the solid-state electrolyte potentiometric sensors have been used for measuring the content of oxygen gas exhausted from automobile engines and flues. Unfortunately, none of the solid-state electrolyte potentiometric sensors that can be applied for measuring the content of oxygen gas dissolved in aqueous solution at room temperature is commercially available to date.
In the meanwhile, as an working electrode of the potentiometric sensor, an ion selective electrode is widely used for quantifying ion and gas species in field of food chemistry, fermentation process, environmental analysis as well as clinical chemistry in relation to blood dialysis, continuous and automatic measurement of blood electrolytes, and extracoporeal circulation of blood. Particularly, analysis of biomaterials in blood plays an important role in modern medical diagnosis.
Recently, chemical sensors for clinical blood analysis have been widely studied in the world. The sensors should give easy, accurate and economic analysis of a sample to be tested. Point-of-care and high sensitivity are also required for allowing health care personnel to perform analysis for themselves and with a small quantity. Further, a microchip-based disposable form and a multi sensor capable of detecting two or more ions and gas species are preferable for universal application.
Leading to the present invention, the intensive and thorough research on oxygen gas sensor, conducted by the present inventors, resulted in the finding that the content of oxygen gas dissolved in a sample solution can be quantitatively determined by measuring corrosion potential produced by the oxidation of cobalt metal and reduction of oxygen.
Therefore, it is an object of the present invention to provide a microchip-type potentiometric oxygen gas sensor capable of quantitatively measuring the content of oxygen gas dissolved in a sample solution.
It is another object of the present invention to determine the conditions under which cobalt metal is introduced to the oxygen gas sensor.
It is a further object of the present invention to provide formulations of a buffered hydrogel and an ion-selective gas-permeable membrane.
It is still a further object of the present invention to provide a microchip-based potentiometric multi-sensor capable of detecting two or more ions or gas species.
These and other objects can be addressed by providing a microchip-type potentiometric oxygen gas sensor comprising a working electrode and a reference electrode, wherein the working electrode is comprised of cobalt-plated electrode, a buffered hydrogel and ion-selective gas-permeable membrane, and the reference electrode is comprised of a Ag/AgCl electrode, which is non-sensitive to oxygen gas and an ion-selective gas-permeable membrane.
The ion-selective gas-permeable membrane in the present invention can be selected from various types of ion selective membranes, preferably hydrogen ion-selective 15 or potassium ion selective membrane 41. Along with the introduction of hydrogen ion selective membrane 15, the reference electrode further comprises a buffered hydrogel layer 14.